14 - wall thickness design example

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Shawn Kenny, Ph.D., P.Eng.

Assistant Professor

Faculty of Engineering and Applied ScienceMemorial University o f Newfoundland

[email protected]

ENGI 8673 Subsea Pipeline

Engineering

Lecture 14: Wall Thickness Design Example


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2 ENGI 8673 Subsea Pipeline Engineering Lecture 14 2008 S. Kenny, Ph.D., P.Eng.

Lecture 14 Objective

to illustrate design example for calculatingminimum wall thickness requirements forpressure containment and local buckling(system collapse)


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Example 14-01

Calculate the minimum wall thickness tomeet (i) pressure containment and (ii)system collapse requirements using DNVOS-F101 (2007) for a subsea oil pipeline

beyond the 500m platform excursion


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EN 8673 Subsea Pipeline Engineering Lecture 14 Winter 2008

Example 14-01

Calculate the minimum wall thickness to meet pressure containment requirements using DNV OS-F101 (2007)for a subsea oil pipeline beyond the 500m platform excursion limit.

DEFINED UNITS

MPa 106Pa:= kPa 10

3Pa:= GPa 10

9Pa:= C K:= kN 10

3N:=

PIPELINE SYSTEM PARAMETERS

Nominal Outside Diameter Do 406.4mm:=

Diameter Out-of-Roundness (Sec.7 G200 Table 7-17) Do 1.6mm:=

Initial Selection Nominal Wall Thickness (Sec.5 C203 Table 5-3) tnom 15.9mm:=

Fabrication Process (Sec.7 B300 Table 7-1) [SMLS, HFW, SAW] FAB "SMLS":=

Corrosion Allowance (Sec.6 D203) tcorr 5mm:=

Elastic Modulus E 205GPa:=

Specified Minimum Yield Stress (Sec.7 B300 Table 7-5) SMYS 450MPa:=

Speciifed Minimum Tensile Stress (Sec.7 B300 Table 7-5) SMTS 535MPa:=

Coefficient of Thermal Expansion T 1.15 105

C1

:=

Poisson's Ratio 0.3:=

Pipeline Route Length Lp 10km:=

Linepipe Density

s

7850kg m3

:=

Concrete Coating Thickness tc 0mm:=

Concrete Coating Density c 3050kg m3

:=

OPERATATIONAL PARAMETERS

API Gravity API 30:=

Product Contents Density

cont 1000 kg m3

141.5

131.5 API+:= cont 876 m

3kg=

Design Pressure (Gauge) Pd 15MPa:=

Safety Class (Sec.2 C200-C400) [L, M, H] SC "M":=

Design Pressure Reference Level h 15


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DNV OS-F101 PARTIAL FACTORS AND DESIGN PARAMETERS

System Operations Incidental/Design Pressure Factor (Sec.3 B304) inc_o 1.10:=System Test Incidental/Design Pressure Factor (Sec.3 B304) inc_t 1.00:=

Material Resistance Factor (Sec.5 C205 Table 5-4) m 1.15:=

Safety Class Resistance Factor (Sec.5 C206 Table 5-5) SC 1.138:=

Material Strength Factor (Sec.5 C306 Table 5-6) U 0.96:=

Maximum Fabrication Factor (Sec.5 C307 Table 5-7)

fab 1.00 FAB "SMLS"=if

0.93 FAB "HFW"=if

0.85 FAB "SAW"=if

:= fab 1.00=

Wall Thickness Fabrication Tolerance(SEC.7 G307 TABLE 7-18)

tfab 0.5mm FAB "SMLS"= tnom 4mmif

0.125 tnom FAB "SMLS"= tnom 4mm>if

0.125 tnom FAB "SMLS"= tnom 10mmif

0.100 tnom FAB "SMLS"= tnom 25mmif

3mm FAB "SMLS"= tnom 30mmif

0.4mm FAB "HFW"= tnom 6mmif

0.7mm FAB "HFW"= tnom 6mm>if

1.0mm FAB "HFW"= tnom 15mm>if

0.5mm FAB "SAW"= tnom 6mmif

0.7mm FAB "SAW"= tnom 6mm>if



:= tfab 1.988 mm=

Material Derating (SEC.5 C300 FIGURE 2)

SMYS T 50 C( )30MPa

50 C

50 C T< 100C


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ENGINEERING ANALYSIS

PRESSURE CONTAINMENT (Sec.5 D200)

Local Incidental Pressure During Operations (Sec.4 B202; Sec.5 D203)

Pli inc_o Pd cont g href hl( )+:= Pli 25.22 MPa=

Local Incidental Pressure System Test (Sec.4 B202; Sec.5 B203 & D203)

Plt inc_t Pd t g href hl( )+ inc_t Pd t g href hl( )+ Pliif

1.03 Pli SC "L"=if

1.05 Pli SC "M"=if

1.05 Pli SC "H"=if

:= Plt 26.48 MPa=

External Hydrostatic Pressure

Pe w g hl:= Pe 10.05 MPa=

Characteristic Yield Resistance - Operations (Sec.5 D203)

fcb_o min fyfu

1.15,

:= fcb_o 417.60 MPa=

Characteristic Yield Resistance - System Test (Sec.5 D203)

fcb_t min SMYSSMTS

1.15,

:= fcb_t 450.00 MPa=

Wall Thickness Requirement - Operations (Sec.5 D202 Eqn.5.7)

t1_o

Do

12

SC m Pli Pe( )2

3 fcb_o+

:= t1_o 8.20 mm=

Minimum Wall Thickness -Operations (Sec.5 C202 Table 5-2)

tmin_o t1_o tfab+ tcorr+:= tmin_o 15.18 mm=

Wall Thickness Requirement - System Test (Sec.5 D202 Eqn.5.7)

t1_t

Do

12

SC m Plt Pe( )2

3 fcb_t+

:= t1_t 8.24 mm=


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Wall Thickness Check - Pressure Containment

tmin_chk

"WT PRESSURE CONTAINMENT OK" tnom

tmin

>if

"INCREASE WALL THICKNESS" otherwise

:=

tmin_chk "WT PRESSURE CONTAINMENT OK"=

Design Wall Thickness Parameters (Sec.5 C202 Table 5-2)

t1_po tnom tfab:= t1_po 13.91 mm=

t1_o tnom tfab tcorr:= t1_o 8.91 mm=

t2_po tnom:= t2_po 15.90 mm=

t2_o tnom tcorr:= t2_o 10.90 mm=

LOCAL BUCKLING (SYSTEM COLLAPSE) (Sec.5 D400)

Elastic Collapse Pressure (Sec.5 D401)

Pel

2 E

t1_po

Do

3

1 2

:= Pel 18.08 MPa=

Plastic Collapse Pressure (Sec.5 D401)

Pp SMYS fab2 t1_po

Do:= Pp 30.81 MPa=

Pipeline Ovality (Sec.5 D401)

fo max 0.0052 Do

Do,

:= fo 0.0079=

Plastic Collapse Pressure (Sec.5 D401)

bpc Pel:= bpc 18.08 MPa=

cpc Pp2

Pp Pel foDo

t1_po+

:= cpc 1077 MPa2=

dpc Pel Pp2

:= dpc 17159 MPa3

=

b2


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pc acosvpc

upc3

180

:= pc 130.579=

ypc 2 upc cospc

3 180

60

180+

:= ypc 9.302 MPa=

Pc ypc

bpc

3:= Pc 15.33 MPa=

Allowable External Pressure Check (Sec.5 D401)

Pe_all

Pc

m SC:= Pe_all 11.71 MPa=

Wall Thickness Check - Local Buckling System Collapse

Pe_chk "WT SYSTEM COLLAPSE OK" Pe

Pc

m SC

if

"INCREASE WT SYSTEM COLLAPSE" otherwise

:=

Pe_chk "WT SYSTEM COLLAPSE OK"=

PROPAGATION BUCKLING (Sec.5 D500)

Propagation Pressure (Sec.5 D501)

Ppr 35 fy fabt2_po

Do

2.5

:= Ppr 4.43 MPa=

Check on Requirements for Buckle Arrestors

PBA_Rqd_Chk "NO BA REQUIRED" Pe

Ppr

m SC


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PBA_WT_chk "BA WT OK" Pe

35 fy fab

t2_po_BA

Do

2.5

1.1m SC


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References

DNV (2007). Submarine Pipeline Systems.Offshore Standard, DNV OS-F101,October 2007, 240p.

14 - wall thickness design example

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